The inventive concept relates to a reliability inspecting method in a high-speed measurement of a fine pattern, and more particularly, a method for inspecting reliability in a high-speed measurement of a fine pattern formed in a photo mask at a high speed.
A design rule of integrated circuits is being reduced to 0.1 micro or below as semiconductor devices are increasingly becoming highly integrated. To produce such semiconductor devices of hyperfine level, various processes are required and margins are increasingly becoming reduced. For example, increasing difficulty in a photolithography processes may cause a serious influence on a wafer due to even small change of a photo mask, and thus an overall investigation for various patterns should be executed on an overall photo mask.
The photo mask undergoes a precise measurement using an electron microscope. However, the photo mask needs to measure by thousands of points or more for the overall photo mask. Meanwhile, an electron microscope SEM is valid to measure just for sampled-pattern at a level of tens of points owing to a speed question. It is also impossible in principle to measure a step coverage or material difference of a photo mask influencing a wafer pattern, an optical difference through an incline of pattern etc., by using an electron microscope.
By such requirement the photo mask is measured at a high speed by using an optical microscope such as an aerial image inspection device. A high-speed measurement method using an optical microscope is to detect a uniformity of a critical dimension (hereinafter, referred to as ‘CD’) of a photo mask pattern by deciding a repetition section for a repeated pattern and obtaining the sum of images therefor and then performing their relative comparison. However, when an open density of pattern is low in the repetition section, a noise-over-signal rate becomes high, thus there maybe difficulty in inspecting a uniformity of CD of a photo mask.